Hi Brenda,
Get yourself a handful of 1N4007 rectifiers and have a ball replacing the old seleniums. A word of caution, though... the rectified DC will be a good bit higher than it would be with good seleniums. If it appears to be unreasonably high after the new diodes have been installed, (along with new electrolytics) get a 6.3 VAC/6A filament transformer, and install it to buck the line voltage on the primary side of the scope's power transformer. That will effectively reduce the AC input to the scope.
Good luck with the restoration!!
Dave M
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On Mon, Nov 5, 2018 at 11:31 AM, <brendda75@...> wrote:
Hello everyone, my name is Brenda and I am new to this forum. A little about
me, I have a general knowledge of electronics but certainly don't know
everything. I had a Tektronix 535A for almost 20 years before life got in the
way. I am "collecting" old tube type scopes to use. I have a RM565, 561 and a
503 that's in working order for the most part. And a few plugins as well. I
have just picked up a Tektronix 531 and it has plenty of issues, the one main
issue is that most of the electrolytics caps are bad. The scope was not on for
a minute and saw some smoke coming from upper section by the high voltage and
shut it down. After that, I felt the electrolytics and most of them were much
warmer than I am comfortable with. I downloaded a manual for the 531, but my
531 has the upgraded board to replace the selenium rectifier. From what I've
read in the forum, Stan stated that the diodes were not the best and would
like to replace them but I can't find what diodes would be best to use. I
would like to replace the diodes and the electrolytics before moving on with
bringing this oldie back to life. Any help would be appreciated. The serial
number on this scope is 8121 and came with a Type M plugin unit.
